1. Technical Field of the Invention
The present invention relates to a three-dimensional locating and displaying system that can suitably be incorporated into such modalities as MR imaging (MRI) systems, and in particular, a three-dimensional locating and displaying system that is capable of setting sections directed to any direction in the three-dimensional image space.
2. Description of Prior Art
In general, in medical modalities such as MR imaging systems, it is frequently required that sections (or volume regions) be placed with desired angles at desired positions in a three-dimensional space, as can be seen in locating sections to be imaged, for example.
Conventional setting of such sections is performed by the following ways. One way is that a reference section is imaged and displayed into a two-dimensional image as a reference image. The reference image is then used to set a section of a region of interest containing an orthogonal vector thereto. For instance, a sagittal plane of an object is first imaged and displayed into a sagittal image as a reference image, then an oblique plane to this image, which is inclined from an axial plane, is set, before the oblique image is imaged.
Another setting way is that a section to be imaged is set, like the foregoing first setting manner, with a two-dimensional reference image being rotated and/or moved by operation to change the reference sections themselves or with an orthogonal section being set to the reference image, using MR continuous scanning (MR fluoroscopy).
A third setting way is a technique that displays a three-dimensional model in the three-dimensional space by the projection method (projection technique), and displays a sectional position existing within the model. Under this condition, using the above-described first or second setting way allows the section to move, thus helping to grasp its spatial position.
However, the above conventional first to third section-setting ways provide poor three-dimensional visibility. Thus it is frequent that positions in the screen are considerably difficult to readily grasp. In this situation, an operator may be unable to quickly understand at which position he has placed or is placing a section, resulting in an inability to select setting of desired sections for imaging in an accurate and quick fashion.
Particularly, in cases where a plane directed to an oblique direction, not perpendicular to a reference image, is set based on the first way of setting, a portion through which the plane intersects with the reference image is displayed as a segment and the remaining portion is displayed by a projected (projected) image. But his method has difficulties in spatial understanding and provides no accuracy in positioning. Even if positions in the three-dimensional space are shown by the third way of setting, an operator must consider the correspondence to a two-dimensional image displayed separately. From a viewpoint that sections should be set at desired positions, this third way of setting is unfortunately not always easy and excellent in maneuverability.
The present invention has been directed towards reducing some of the drawbacks that the foregoing conventional section setting ways possess. One object of the present invention is to provide a section setting technique capable of setting a section at desired three-dimensional positions in a speedy, accurate and easy fashion with the spatial-position relationship between an object and its region to be scanned recognized accurately.
Another object of the present invention is, with a section set according to the above manner, to display a real-time image at the region to be scanned and provide it for observation.
To achieve the above objects, a basic feature of the present invention is that a three-dimensional locating and displaying system comprises region display means for displaying at least one region placed in a three-dimensional space set within an object; image display means for displaying at the region an image at a portion of the object corresponding to the region; and change means for arbitrarily changing at least one of a direction and a position of the region in the three-dimensional space. For example, the region is a volume-like region or a sectional region. Preferably, the region display means display both the sectional region and three-dimensional absolute coordinate axes set in the three-dimensional space. Thus an operator is able to easily locate the region as observing the region residing in the three-dimensional absolute coordinate.
Particularly, one preferred example is that, the region to be scanned is a sectional region, and the system comprise scanning means for obtaining a two-dimensional image by continuously scanning (fluoroscopy) the sectional region and pasting means for pasting the two-dimensional image on the sectional region displayed in the region display means successively in real time. Thus an operator is able to set the position of a section to be scanned as understanding a spatial relationship between the operator and the section to be scanned.
According to another preferred example, there may be provided reference image display means for pasting, as a reference image, the two-dimensional image scanned at any time on another sectional region placed in the coordinate system. By referring to this reference image, an operator can grasp more easily a spatial relationship between the object and the section to be scanned, locating the section more accurately.
According to still another preferred example, there are provided specifying means for specifying a position in the three-dimensional space; and marker display means for displaying a marker in the three-dimensional space, the marker corresponding to the specified position. For example, the marker display means displays the marker in a different hue from the two-dimensional image. This makes it possible to effectively use techniques, such that a section to be scanned is moved to the position of the marker, thereby assisting the location of the section.
According to still another preferred example, the position change means are constituted by means for specifying the sectional region into a desired three-dimensional position by a moving operation, a rotary operation and a moving operation. Thus a series of images can be scanned with sections that undergo offsets continuously rotated.
Still preferably, means capable of not merely time-sequentially recording three-dimensional positions of the region in the three-dimensional space but also calling the recorded three-dimensional positions are provided. Means for time-sequentially replaying the two-dimensional image corresponding to the called three-dimensional position may also be provided.
Still, a preferable embodiment is that the position change means changes a position of the sectional region for the continuos scanning in a predetermined stylized operation. For example, the stylized operation uses, as a technique for specifying a move amount of the sectional region, a macro description with a function of time. In addition, by way of example, the position change means automatically sets, by image processing, a vector concerning a move direction of a position of the sectional region in the continuous scanning, thereby determining the position automatically. This provides an easy-to-operate-locating manner.
Further, in a preferred example, there are provided two-dimensional display means for two-dimensionally displaying the two-dimensional image; and landmark display means for displaying in the three-dimensional space a landmark indicating a direction along which the two-dimensional image is observed. This upgrades the assistance capability for locating the section.
Preferably, there are specifying means for specifying a slice direction in which the object is scanned; continuous scanning means for producing a plurality of two-dimensional images by continuously scanning an entity to be scanned containing the region of the object along the slice direction; and locating image producing means for producing from the plurality of two-dimensional images a locating reference image of the entity, the locating reference image being outlined into a three-dimensional image. For example, the locating image producing means extracts contours of the entity from a plurality of images and produces the reference image from data of the contours.
Further, preferably, there is provided a construction which includes: signal detecting means for detecting a signal expressing physiological information about the object; scanning means for scanning an entity to be scanned containing the region of the object in association with the signal of which time elapses; and signal displaying means for displaying, together with the signal, a marker indicating that an image scanned by the scanning means corresponds to which timing in the signal, wherein the image display means displays the image scanned by the scanning means synchronously with the signal displayed by the signal display means. For instance, the signal expressing physiological information about the object is an ECG signal. Additionally, a construction that both the signal display means and the image display means operates during scanning by the scanning means or at replay after the scanning by the scanning means may be provided.
Still one preferred example is to provide scanning means for continuously scanning a plurality of portions containing the region of the object; and locator providing means for providing a plurality of locators using real-time images scanned by the scanning means. By way of example, with the region being a section, the locator providing means provides each locator including one section on which the real-time image scanned by the scanning means is displayed by giving the real-time image for the image display means and the other section, intersected with the one section, on which a reference image is pasted.
Further, the three-dimensional locating and display image can be, as one example, incorporated into an MRI system.